This invention relates to air and vacuum relief valves, and more particularly to a new and improved air and vacuum relief valve primarily intended for use in venting air to and from an irrigation water supply line.
In many pressurized water supply lines such as, for example, those used in irrigation, it is highly desirable to prevent the formation of air blocks in the line by venting air from the line during filling of the system. On draining of the system, it may also be desirable to vent air back into the supply line to prevent the formation of a vacuum in the line which could cause the line to collapse.
Various air vent and vacuum relief valves have been proposed in the prior art to protect against air blockage and vacuum collapse of a water supply line. Typically such prior art valves include a housing connected to the high point of the water supply line and within which is mounted a cylindrical or sphirical float body. On filling of the line, air is vented from the line through the valve until water enters the housing and raises the float body to close the valve. On draining of the line, water within the housing recedes, causing the float body to drop and open the valve for admitting air back into the line.
While such prior art valves have met with some degree of commercial success, none has been totally satisfactory. One significant problem that has been encountered is that of pre-mature valve closure caused by high air flow rates through the valve on line filling. In many prior art valves, the float body is relatively light in weight and has a right cylindrical or sphirical shape presenting a relatively high coefficient of drag. With such float bodies, high air flow rates through the valve may prematurely lift the float body and close the valve before all air has been vented from the supply line. Although attempts have been made to design a valve that will not prematurely close due to high flow rates, such as valves have typically required baffles and shields which are expensive to manufacture and complex in design.
Thus, there exists a need for a reliable and effective air and vacuum relief valve which is simple in design and economical to manufacture yet which will not prematurely close in the presence of high air flow rates through the valve. As will become more apparent hereinafter, the present invention satisfies this need.